Engineering Contracts And Specifications

SPECIFICATIONS FOB STEEET PAVEMENTS, ETC. 185
If rock asphalt be used, it must be natural bituminous limestone rock: (i) from the Sicilian mines at Ragusa, equal in quality and composition to that mined by the United Lim-mer and Ver Wohle Rock Asphalte Company, Limited; (2) from the Swiss mines at Val de Travers, equal in quality and composition to that mined by the Neuchatel Rock and Asphalte Company, Limited, or (3) from^the French mines at Seyssel, equal in quality and composition to that mined by the Com-pagnie Generale des Asphaltes de France, and it shall be prepared and laid as follows:
(i) The lumps of rock shall be finely crushed and pulverized, the powder shall then be passed through a fine sieve. Nothing whatever shall be added to or taken from the powder obtained by grinding the bituminous rock. The povvder shall contain from nine to twelve per cent, natural bitumen, eighty eight to ninety one per cent, pure carbonate of lime, and must be free from quartz, sulphates, iron pyrites, or aluminum. (2) This powder shall be heated in a suitable apparatus to two hundred or two hundred and fifty degrees Fahrenheit, and must be brought to the ground at such temperature in carts made for the purpose, and then carefully spread on the foundation previously prepared, to such depth that, after having received its ultimate compression, it will have a thickness of two inches. (3) It shall be skillfully compressed by heated rammers and rolled until it shall have the required thickness of two inches. (4) The surface to be rendered perfectly even by heated smoothers, and to be rolled with a steam roller weighing not less than two hundred and fifty pounds to the inch run, the rolling to continue for not less than five hours for each one thousand yards of surface. A. P. B.
137. Specification for Granite Pavement. The following specification for granite pavement is that used in the city of Milwaukee so far as the granite paving is concerned. These granite blocks are laid upon a concrete foundation six inches thick, and this latter upon a carefully prepared surface which has been thoroughly rolled with a he'avy roller. The concrete is made of natural cement one part, sand two parts, and broken stone five parts. On this is spread a sand cushion two inches thick when compacted, on which the granite blocks are laid.
Granite Block Paving. The blocks must consist of a hard granite uniform in grain and texture, without lamination or stratification and free from excess of mica or feldspar. Neither hard basaltic stone that will take a smooth polish under traffic,